/*
Copyright 2017 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package cmd

import (
	"fmt"
	"io"
	"os"
	"os/signal"
	"runtime"
	"runtime/pprof"
	"runtime/trace"

	"github.com/spf13/pflag"
)

var (
	profileName   string
	profileOutput string
)

func addProfilingFlags(flags *pflag.FlagSet) {
	flags.StringVar(&profileName, "profile", "none", "Name of profile to capture. One of (none|cpu|heap|goroutine|threadcreate|block|mutex|trace)")
	flags.StringVar(&profileOutput, "profile-output", "profile.pprof", "Name of the file to write the profile to")
}

// initProfiling inits profiling and returns a function to be called on exit to flush and close.
func initProfiling() (func() error, error) {
	var (
		f   *os.File
		err error
	)
	switch profileName {
	case "none":
		return nil, nil
	case "cpu":
		f, err = os.Create(profileOutput)
		if err != nil {
			return nil, err
		}

		err = pprof.StartCPUProfile(f)
		if err != nil {
			f.Close() //nolint:errcheck
			return nil, err
		}
	// Block and mutex profiles need a call to Set{Block,Mutex}ProfileRate to
	// output anything. We choose to sample all events.
	case "block":
		runtime.SetBlockProfileRate(1)
	case "mutex":
		runtime.SetMutexProfileFraction(1)
	case "trace":
		f, err = os.Create(profileOutput)
		if err != nil {
			return nil, err
		}

		// Enable the CPU profiler. Samples will be captured in the execution trace.
		// This is the same rate value as used in pprof.StartCPUProfile.
		runtime.SetCPUProfileRate(100)
		if err := trace.Start(f); err != nil {
			f.Close() //nolint:errcheck
			return nil, err
		}
	default:
		// Check the profile name is valid.
		if profile := pprof.Lookup(profileName); profile == nil {
			return nil, fmt.Errorf("unknown profile '%s'", profileName)
		}
	}

	// If the command is interrupted before the end (ctrl-c), flush the profiling files
	c := make(chan os.Signal, 1)
	signal.Notify(c, os.Interrupt)
	go func() {
		<-c
		flushProfiling(f) //nolint:errcheck
		os.Exit(0)
	}()

	return func() error {
		return flushProfiling(f)
	}, nil
}

func flushProfiling(output io.Closer) error {
	if output != nil {
		defer output.Close() //nolint:errcheck
	}

	switch profileName {
	case "none":
		return nil
	case "cpu":
		pprof.StopCPUProfile()
	case "trace":
		trace.Stop()
		runtime.SetCPUProfileRate(0)
	case "heap":
		runtime.GC()
		fallthrough
	default:
		profile := pprof.Lookup(profileName)
		if profile == nil {
			return nil
		}

		f, err := os.Create(profileOutput)
		if err != nil {
			return err
		}

		defer f.Close()
		profile.WriteTo(f, 0)
	}

	return nil
}